The Nigerian military has begun operations against the Islamist militant group Boko Haram, using fighter jets and helicopter gunships. Thousands of people have died in Boko Haram attacks and associated sectarian violence in recent years. However there are some doubts over the effectiveness of an all-out military response.
Declaring a state of emergency in three northeastern states Tuesday, Nigerian President Goodluck Jonathan ordered security forces to take all necessary action.
"Whoever they may be, wherever they may go, we will hunt them down, we will fish them out, and we will bring them to justice," he said. "No matter what it takes, we will win this war against terror."
Nigerian troops are already part of the international force currently fighting Islamist insurgents in Mali.
Past experience suggests it will be difficult to eradicate the Boko Haram insurgency on Nigerian territory, said Elizabeth Donnelly, assistant head of the Africa Program at London-based policy institute Chatham House.
Major attacks blamed on Nigeria's Boko Haram
July - Attacks prompt government crackdown in Bauchi and Maiduguri; 800 people killed
December - Bombings in central Nigeria and church attacks in the northeast kill 86
June - Attack on a bar in Maiduguri kills 25
August - Suicide bomber kills 23 at U.N. building in Abuja
November - Bombings in Damaturu and Potiskum kill 65
December - Christmas Day bombings across Nigeria kill 39
January -- Gun and bomb attacks in Kano up to 200
February - Maiduguri market attack kills 30
June - Suicide car bombings at three churches kill 21
July - Attacks in Plateau state kill dozens, including two politicians at a funeral for the victims
February - French family kidnapped in Cameroon, held hostage for two months
April - Fighting with troops in Baga kills up to 200; residents say troops set deadly fires
May - Attacks in Bama kill more than 50
July - Gunmen kill 30 at a school in Yobe
August - Gunmen kill 44 at a mosque outside Maiduguri
September - Gunmen kill 40 students at a post-secondary school in Yobe
December - Militants attack military installations in Maiduguri
January - Militants kill 74 people and burn down a village in attacks in Borno and Adamawa
February - Gunmen kill as many as 60 in attack on school in Yobe
April - Militants abduct 276 schoolgirls
"It is not a change in strategy. It is an intensification of strategy," she said. "And there have been a lot of complaints about the significant use of force in the past and that it hasn't actually achieved anything. In fact you've seen a strengthening of Boko Haram."
Donnelly said the military risks being drawn into a long campaign against an elusive target.
"These states that are under the state of emergency all border Nigeria's neighbors - Chad, Cameroon, Niger - and that goes back to the question of sustainability and effectiveness," she said. "Is it possible that members [of Boko Haram] might simply be displaced and return?"
The north of Nigeria has been neglected for too long by central government, said Virginia Comolli, a Nigeria analyst at the International Institute for Strategic Studies.
"Because things have been neglected and downplayed for so long it also means that the situation has degenerated so much, that now a military component to the strategy is inevitable," she said.
Comolli said the high youth unemployment in northern cities like Kano acts as fertile ground for extremism.
"They are likely to remain on the streets, carry on as beggars because that's also what they do during their so-called education," she added. "And some of them join criminal groups and perhaps also more extremist groups. Not so much because they espouse the extreme ideology but because these groups may offer them the chance to channel their grievances and also to make some money."
Since an escalation in attacks in 2009, Boko Haram has targeted Christian churches and villages. There have been reprisal attacks on Muslims and allegations of abuses by the military.
"They are very afraid of Boko Haram and Boko Haram-related violence," said Donnelly of Chatham House. "But they're also very afraid of the joint task force that is present in the northeast of Nigeria. And further to these abuses of course it's economic matters, people just cannot go about their daily lives."
The state of emergency in the northeast lasts for six months. Analysts say the military operation could take much longer.
(In a previous version of this story, Elizabeth Donnelly was incorrectly identified as Elizabeth Connelly.)